Dehydration and decomposition of iron sulphates



Pas ed July 1, 1931 UNITED STATES PATENT OFFICE PAUL WEISE, OIWIESDOBF-ON-IHE-BHINE, GEBI ANY, ASSIGKOR '10 1'. G. FABBEN OFrmxronr-oN-rnn-m, GERKAJNY, A

INDUSTBIE AKTIEN'GESELLSCHAFT, CORPORATION OI GEBM'ANY DEHYDBA'IION ANDDECOMEOSITION 0! IRON SULPH Am Io Drawing. Application filed January 5,1929, Serial No. 830,621, and in Germany January 9, 1928.

The present invention relates to a process for the dehydration anddecomposition of iron sul hates. i

The d ehydration and decomposition of the ferrous sul hate,crystallizing with seven molecules'of water, proceeds in three stages,if this compound is heated in an oxid zmg atmosphere such as air; first,thesalt is dehydrated, then the salt oxidizes to form ferr1c salt, andthen the ferric salt decomposes to form S0 and ferric oxide.

The technical dehydration and decomposition of iron sulphates,especially of ferrous sulphate FeSO 7H O, in mechanical ovens sufieredfrom various disadvantages up to this day.

As FeSOJH O, when being dehydrated,

1 melts in its own water of crystallization, me-

chanical ovens, especially the rotary furnace, could not be usedheretofore, since either the melted mass passed unhindered through therotary furnace or adhered tenaciously to the wall and caused the oven ina short time to smear or become greasy and clog up. For these reasons,it has also been impossible to carry out any oxidation processsubsequent to the dehydration or subsequent to the-decomposition.Furthermore, the processes suffered from the disadvantage thatdecomposition roducts, as SO dissociated into S0 and 2 on account of thehigh decomposition temperature; Consequently, only poor yields of S0could be obtained. I 1

According to the present inventionthese disadvantages are removed byadding to the 'ferrous sulphate to be dehydrated a substance whichdlmlnishes the plasticity and which does not prejudicially interferewith the kind and quality of the solid decomposition prodnot, the mostfavorable substance for the purpose of my invention being the partiallydehydrated ferrous sulphate of the formula: FeSO .1H O, or ferric oxide,which latter acts in myprocess at the same time as an oxidizingcatalyst. The quantity of the substance diminishing the plasticitymay bevaried within wide limits, at least about 10% calculated on the amountof the ferrous sulphate bein required generally, I add an amount of omabout 10% to about 30%. 7

As the S0,, evolved at the decomposition temperature of the ferric salt,partially dissociates in'to S0 and 0 an oxidizing catalyst to 5%, suchas an-alkalior alkaline earth metal oxide, hydroxide or carbonate,whereby an eva oration of the sulfuric acid is hindered; ee sulfuricacid would unfavorably influence the quality of the ferric oxideobtained in my process.

My process may preferably be performed in a rotary furnace, in which theupper part acts as dehydrating .zone, the medium part as oxidizing zone,and the lower parts as decomposing zone. The best results are obtainedin using at least three separated rotary furnaces, the first furnacebeing heated to-a temperature of from about 100 to about 200 C. andserving to dehydrate the ferrous sulphate to form F eSO H O, the secondfurnace being directly heated with oxidizing gases to about 300 to 400C. and serving to form ferric sulphates, and the third rotary furnacebeing indirectly heated to about 750 to about 800 C.

According to my process it is possible to work up ferrous sulphate in a.mechanical oven into ferric oxide suitable to be used as a pigment andto recover almost completely the sulfuric acid in the form of S0 Theinvention is illustrated by the following examples, without beinglimited thereto:

ing, the mixture is placed in a second rotary furnace in which it isslowly heated through one or more stages and 1n an oxidizing atmosphereup to a temperature of about 300 to 400 0., to form ferric sulphate. Theferric compound is placed in a thlrd rotary furnace wherein it isindirectly heated to the decomposition temperature of the ferric salt,for instance to 750 to 830 0. Llght iron oxide, suitable to be vused asa igment, is obtained and at the upper end 0 the rotary furnace SOescapes.

E wmmple 2.Ferrous sulphate (FeSO 7H O) (with the addition of FeSO, or25% FeSO .1H O is mixed with 1% of sodium carbonate and, dependingon'the amount of F eSO.or.FeSO .1H O further, is mixedwith 10-30% byweight of-iron oxide and treated as described in Example 1.

I claim 1. In the process for the dehydration and decomposition of ironsulphates the step which comprises heating a mixture of Iron sulphateand 10-30% of a solid, iron-containing decomposition product of lronsulphate, to a temperature of between about 100-200 0.

2. In the process for the dehydratlon and decomposition of ironsulphates the step which comprises heating a mixture of iron sulphateand 10-30% of a solid, iron-containing decomposition product of ironsulphate, to a temperature of between about 100200 0. in a rotaryfurnace.

3. In the process for the dehydration and decomposition of iron sulphatethe step which comprises heating a mixture of iron sulphate and 10-30%FeSO .1H O to a temperature of between about 100-200 0.

t. In the process for the dehydration and decomposition of iron sulphatethe step which comprises heating a mixture of iron sulphate and 10-30%FeSO .1H O to a temperature of between about 100-200 0. in a rotaryfurnace.

5. The process decomposition of iron sulphates which comprises heating amixture of iron sulphate and 10-30% of at least one solid,iron-containing decomposition product of iron sulfate, to a temperatureof between about 100-200 0., heating the dehydrated mixture in anoxidizingatm'osphere to a temperature of between about 300-400 0. in thepresence of anoxidizing catalyst, and heating the oxidized mixture to atemperature of between about 750830 0.

6. The process for the dehydration and decomposition of iron sulphateswhich comprises. heating a mixture of iron sulphate and 10-30% of amixture of FeSO .1H O

and iron oxide (Fe O to a temperature of between about 100-200 0.,heating the dehydrated mixture in an oxidizing atmosphere to atemperature of between about 300-400 0., and heating the oxidized mixforthe dehydration and ture to a temperature of between about 750-830 0.

7. The process for the dehydration and decomposition of iron sulphateswhich comprises heating a mixture of iron sulphate and 10-30% of atleast'one" solid iron-containing decomposition product oi iron sulphate,to a temperature of between about 100-200 0., heating the dehydratedmixture in an oxidizing atmosphere to a temperature of between about300-400 0. inv the presence of an oxidizing catalyst, and heating theoxidized mixture to a temperature of between about 750-830 0., the threeheating processes being efiected in rotary furnaces.

8. The .process for the dehydration and decomposition of iron sulphateswhich comprises heating a mixtureof iron sulphate and 10-30% of amixture of FeSO II-I O and-iron oxide (Fe O to a temperature of betweenabout 100-200 0., heating the demy hand.

PAUL WEISE. [net]

